We have many of those too. Some the size of a small car.
The head size rocks that I mentioned earlier is the size the retailer prefers.
Ah, got it. That makes sense. I am dealing with a "small-car" size one right now. Not sure how to proceed. Was thinking of digging a large hole right next to it, and let it drop down into the ground further, so it's fully buried. Alternatives are to rent a rock hammer, or to blast it.
(sorry to hijack this thread from a cordless hole drill-bit to rocks in PA! )